Promotion of dithionate ion formation in leaching oxidic manganese ores with sulfur dioxide solutions



Patented June 17, 1952 UNITED STATES PATENT OFFICE PROMOTION OFDITHIONATE ION FORMA- TION IN LEACHING OXIDIC MANGANESE ORES WITH SULFURDIOXIDE SOLUTIONS tary of the Interior No Drawing. Application-December30, 1948, Serial No. 68,382

(01. 23-115) (Granted under the act of March 3, 1883, as amended April30, 1928; 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or forthe Government of the United States for governmental purposes withoutthe payment to us of any royalty thereon in accordance with theprovisions of the act of April 30, 1928 (ch. 460, 45 Stat. L. 467).

This invention relates to the reactions of the system manganesedioxide-sulfur dioxide-wateroxygen. Particularly the invention relatesto a method for catalytically controlling the reactions of this systemso as to increase the rate of dithionate ion formation.

The dithionate process for the recovery of manganese from low-grade oreshas been described by Ravitz, Wyman, Back, and Tame in TechnicalPublication No. 2064 of the American Institute of Mining andMetallurgical Engineers (Class D, Metals Technology, September 1946),and also in the patent application of F. s. Wartman and Wallace F.Wyman, Serial No. 744,532, filed April 28, 1947, now abandoned. Thedithionate process utilizes the following reactions of the systemmanganese dioxide-sulfur dioxidewater-oxygen:

In the process, a slurry of the oxidic manganese ore in an excess ofcalcium dithionate solution is treated with gas containing sulfurdioxide and oxygen. Manganese sulfate, manganese dithionate, sulfuricacid, and dithionic acid are formed in the above reactions. The sulfateion formed by reactions (1) and (3) is immediately precipitated ascalcium sulfate by reaction with the suspending calcium dithionatesolution:

The intermediate oxides M11203 and M11304, which may be present in theore, behave largely as though they were mixtures of M1102 and MnO, thelatter being dissolved by the acid formed in reactions (3) and (4)MnO+2H+=Mn+++HzO (6) At the end of the leaching process the solids,

which consist .of the insoluble portion of the ore and the precipitatedcalcium sulfate, are separated from the solution and discarded (ortreated further if they contain appreciable quantities of lead, gold, orsilver). The solution which contains manganese dithionate, a smallquantity of dithionic acid, and the excess of calcium dithionate, istreated with slaked lime to precipitate manganese hydroxide andregenerate the calcium dithionate:

The precipitate is filtered off and nodulized or sintered to producemanganese oxide, and the calcium dithionate solution is recycled. Thedithionate losses are those due to incomplete washing of the leachresidue and the manganese hydroxide precipitate. To maintain thedithionate concentration in the circuit, the quantity of dithionateformed by reactions (2) and (4) should at least be equal to such losses.Therefore it is highly desirable to be able to control the rate ofdithionate formation. In the aforementioned Wartman and Wymanapplication, the rate of formation of sulfate, dithionate, and acid iscontrolled in the system manganese dioxide-sulfur dioxide-water-oxygenby controlling at least one of the following conditions: the ratio ofoxygen to sulfur dioxide in the gaseous treating mixture; the depth ofthe ore pulp being treated; and the bubble size of the gaseous treatingmixture.

While the varyin of these reaction conditions has been found to beeffective in controlling the rate of dithionate, acid, and sulfateformation, it is felt that a more simplified technique to accomplishthis function would be more desirable.

Accordingly, it is an object of this invention to devise a simplifiedprocess for the control of the rate-of formation of dithionate, sulfate,and. acid in the system manganese dioxide-sulfur dioxidewater-oxygen. Itis another object to present an improved dithionate process for therecovery of manganese from low -grade manganese ores.

Other objects and advantages will be apparent or will appearhereinafter.

These objects and advantages are accomplished in accordance with thisinvention wherein petroleum fractions are employed to catalyze thereactions of the manganese dioxide-water-sulfur dioxide-oxygen systemwhereby the rate of dithionate formation is increased.

In the discussion to follow the system manganese dioxide-water-sulfurdioxide-oxygen is not to be construed as being limited to the quaternarysystem recited. Other materials can be present for example: themanganese dioxide can be present as an impure manganese ore containingmanganese dioxide along with the various matrix materials; the water canalso be a solution such as the alkali earth metal dithionate solutionused in the cyclic dithionate process; the sulfur dioxide can be wastesmelter gases or other mixtures containing S02; and the oxygen can besupplied as air or other mixtures containing elemental oxygen.

Suitable petroleum fractions for use as catalysts in accordance withthis invention include the pure hydrocarbons separable from petroleumsuch as dodecane, tetralin, n-butyl cyclohexane, and the like; andmixtures thereof such as heavy lubricating oil, kerosene, gasoline, fueloil, hy draulic oil, light machine oil, and the like.

These petroleum fractions can be employed in any suitable manner eitherin pure form or when combined with a suitable emulsifying or dispersingagent. Since the use of emulsifying agents and the like appear to permita more uniform dispersion of the petroleum fraction throughout ventionmay be carried out but it is not limited thereto. In these examples alaboratory leaching apparatus was constructed to permit sulfur dioxideleaching of samples of manganese ore under reproducible conditions. Thegeometrical position of all the apparatus in the cell was fixed; theagitator speed was held constant at 495:5 R. P. M.; the gas inlet wasmade from 10 mm. (0. D.) glass tubing placed so that the gas wasdischarged in the direction that the agitator turned and at a point ,4;inch above the agitator blade and 1%}; inches from the agitator shaft;the slurry depth was 5%; inches; the gas rates were held constant withthe aid of valves and fiowmeters at 0.08 pound of sulfur dioxide perhour and 155:0.2 cubic feet of air per hour, respectively; and thetemperature was held constant at :0.50 centigrade. Two-hour leachingtests were made under the above standardized conditions. In each test1.14 grams of sulfur dioxide was introduced per gram of manganeseintroduced. Similar ore samples were obtained by rifiiing all thesamples from the same well mixed minus 65-mesh lot. The manganese yvaspresent as pyrolusite, psilomelane, manganite, braunite, and wad, andhad the following composition:

TABLE 1 Oz. per ton Mn Zn Fe Cu CaO MgO A120: Insol Au Ag Per Per PerPer cent cent cent cent Per cent Percent Per cent Per cent 15.2 1.251.55 0.12 0.15 0.2 2.1 67.6 0.005 11.3

the reaction mixture and thereby permit the use EXAMPLE I of smallerquantities of the catalyst, it is presently preferred to employ anemulsifying agent along with the petroleum fraction. The followingemulsifying agents summarize in part those which have been foundsatisfactory in this connection but the process is not to be consideredas limited thereto; soaps, a sulfated monoglyceride of coconut oilderivation (Syntex M), the ammonium salt of lauryl diethylene glycolsulfate (Emulsol X-l) sodium isopropyl naphthylene sulfonate (AerosolOS) sodium oleate, and the like.

In operation the petroleum fraction is dispersed throughout themanganese dioxide-water slurry or pulp. When added'in pure form betweenabout 1 to 40 pounds of the catalyst per ton of manganese ore has beenfound to function satisfactorily. Although greater or lesser quantitieswill be found operable, depending to some extent on other conditions ofthe process as shown in the Wartman and Wyman application.

The catalyst can also be added as an emulsion and, when so added, theemulsion can be readily prepared by known methods using suflicientemulsifying reagent and water to prepare an emulsion that can be readilydispersed throughout the ore-water pulp. In such instances between about0.01 to 1 pound of catalyst per ton of manganese ore have been found tobe effective; but while these quantities, too, have been found capableof being varied within much wider limits, economic factors will be foundto be sound limitation. V r

The following examples will show how the in- Using the leaching cell, orsample, and procedure described in the preceding paragraphs, tests weremade as to the effect of adding kerosene (40 pounds per ton of ore) tothe ore slurry, and these results were compared with test runs in whichno catalysts were added. The results are summarized in part in Table 2below.

TABLE 2 The efi'ect of kerosene on dithionate formation Per cent Con-523 was assert. a m

urmg

to test None l4. 0 1. 89 9. 7 None 14. 4 1. 88 10. 5 None l4. 2 l. 8810. 6 Kerosene (40 lbs/T ore) 51. 8 3.0 30. 2

EXAMPLE II Comparable tests were carried out employing other petroleumfractions as catalysts. The data from these tests are compared with thestandard runs without a catalyst in Example I. The results are in partsummarized in Table 3 below.

Quid; be

Final pH deviation from standard, in pH units lcaches S utilization Percent of values obtained in standard 09709110979983398532548 WMMWOQOXUQOOOQQQQ99999900999 1 11 1 111 11 Additional data on tests inwhich emulsified fier TABLE 5 fie'd, and that an emulsifying agent 0used to give a, stable emulsion witho ciablly' affecting the action ofthe catalyst. is to be noted. that the results with 1 pound of fuel oilper ton: of ore, when the on. was emulsi- Yes fied, were nearly as goodas'those with 12- pounds per ton, when the oil was not emulsified.

fuel oil was used are given in: Table 5.

acetate- Conversion of absorbed Weight ra- Percent of the valuesobtained in the standtracoil Lb. per ton of ore Fuel Emulsi- 11111111111111111111111111100000001 0 0 QO QQQQQQQQQQQQQQQQQQQQQQQQ Yes FuelEmulsioil Emulsion concentratlon, per cent The results are com-Laboratory teaches whereinemulstfied fuel used;

TABLE 4 fracti us not emulsified were used,

7 Lb. catalyst per ton of ore Mn exper cent Test No.

The efiect of emulsifying the catalyst Test N 0.

Laboratory leaching tests wherein petroleum Catalyst Gasoline.

Kerosene Fuel oil Hydraulic oil. Machine oil.

Further comparable tests were carried out us-' fuel oil as the catalyst,together with vari- Mn extraction. S utilization Weight ratio:

Conversion of absorbed SO: Final pH deviation. from the standar The dataof Table 4 show, in the case of fuel oil, that when the catalyst wasemulsified high dithionate formation could be achieved with lessstandard leaching tests:

in pH units 1 The ammonium salt of lauryl methylene glycol sulfate(Emulsol X-l).

catalyst than when the catalyst was not emulsi- Heavy oil ifrg ousemulsifying agents.

pared with those in Examples I and II, and are summarized in part inTable 4 below.

Pounds of fuel oil per ton of ore Emulsion concentration Pounds ofemulsifier per ton of ore.

Per cent of the values obtained in the 1 Syntax M is a trade name for asulfated monoglyceride of coconut oil derivation, Emulsol X-l" for theammonium salt of lauryl diethylene glycol sulfate. The composition ofEmulsol tri-X is not known.

From the foregoing description and examples, it is apparent that whenthe various petroleum fractions are employed as catalysts in the systemmanganese dioxide-sulfur-dioxide-wateroxygen, the rate of dithionateformation is increased and the rate of sulfate and acid formation isdecreased.

It is desirable and advantageous to increase the formation of dithionateion, particularly in commercial application of this invention. Thefactors inhibiting dithionat formation, particularly in a commercialsize operation of the process of this invention, far out-weigh thefactors promoting dithionate formation, and any catalyst which increasesdithionate formation is an asset to the process. The reactions areexothermic and an eflicient cooling system is required to maintain theslurry temperature below 50 C. The successful operation of this processrequires that suflicient dithionate be formed to offset washing lossesand to give a pregnant solution relatively free from sulfate ion so thatthe final manganese product will not contain excess lime or sulfur fromthe coprecipitated gypsum.

Since many widely differing embodiments will be apparent to one skilledin the art, various changes can be made therein without departing fromthe spirit and scope thereof.

What is claimed is:

1. In a process for the recovery of manganese values from oxidicmanganese ores comprising the steps of forming a slurry of manganeseore, treating said slurry with S02, separating the insoluble materialfrom the solution, and precipitating manganese values from saidsolution, the improvement which consists in adding petroleum fractionsso as to promote dithionate ion formation in the S02 reaction.

2. In a process for the recovery of manganese values from oxidicmanganese ores comprising the steps of forming a slurry of manganeseore, treating said slurry with S02, separating the insoluble materialfrom the solution, and precipitating manganese values from saidsolution, the

improvement which consists of adding a mixture of petroleum fractionsand an emulsifying agent so as to promote dithionate ion formation inthe S02 reaction.

3. In a process for the recovery of manganese values from oxidicmanganese ores comprising the steps of forming a slurry of manganeseore, treating said slurry with $02, separating the insoluble materialfrom the solution, and precipitating manganese values from saidsolution, the improvement which consists of adding from one to fortypounds of a, petroleum fraction per ton of manganese ore treated so asto promote dithionate ion formation in the S02 reaction.

4. In a process for the recovery of manganese values from oxidicmanganese ores comprising the steps of forming a slurry of manganeseore. treating said slurry with S02, separating the insoluble materialfrom the solution, and precipitating manganese values from saidsolution, the improvement which consists of adding a mixture of from oneto forty ounds of a petroleum fraction and 0.01 to one pound of anemulsifying agent per ton of manganese ore treated so as to promotedithionate ion formation in the S02 reaction.

WALLACE J. WYMAN. Administrator 0 f the Estate of Wallace F. Wyman,

Deceased.

ALEXANDER E. BACK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,325,129 Westling Dec. 16. 1919FOREIGN PATENTS Number Country Date 51,258 Sweden June 21. 1920 28,865Denmark Nov. 16, 1921 OTHER REFERENCES Mellor, Modern InorganicChemistry, pp. 456, 457, London, Longmans, Green 8: Co., 1920.

1. IN A PROCESS FOR THE RECOVERY OF MANGANESE VALUES FROM OXIDICMANGANESE ORES COMPRISING THE STEPS OF FORMING A SLURRY OF MANGANESEORE, TREATING SAID SLURRY WITH SO2, SEPARATING THE INSOLUBLE MATERIALFROM THE SOLUTION, AND PRECIPITATING MANGANESE VALUES FROM SAIDSOLUTION, THE IMPROVEMENT WHICH CONSISTS IN ADDING PETROLEUM FRACTIONSSO AS TO PROMOTE DITHIONATE ION FORMATION IN THE SO2 REACTION.